Heart Care

Abnormal Heart Rhythm May Be Predicted By Risk Score

Weighing a combination of risk factors could help doctors predict which patients are the most likely to develop atrial fibrillation, says a study reported in the medical journal The Lancet.

Researchers have developed a risk score that might one day help prevent what has become the most common type of abnormal heart rhythm in the US, affecting about 2.2 million people.

An Increase In AF Prompts Probe

Atrial fibrillation, or AF, is a condition that causes the upper chambers of the heart to beat erratically, which hinders the heart's ability to pump blood. It can increase the risk of stroke, heart failure, and dementia. According to the American Heart Association, AF can be controlled with medication or surgical procedures, but there is no way to keep it from developing so far.

"We know a lot about the prevention of many different types of vascular disease, but there has been very little attention paid to preventing AF," says lead researcher Dr. Emelia Benjamin, at Boston University School of Medicine.

But attention might be warranted, since the condition is on the increase in the US. By 2050, almost 16 million Americans will have AF, says Dr. Benjamin. This dramatic increase is partly due to people living longer and developing diseases associated with aging. In addition, people with heart disease are also living longer.

A Closer Look at Risk Factors

"The risk factors for AF are known, but they tend to be looked at one at a time, and there has been no way of predicting an individual's risk for the disease, says Dr. Benjamin."

"We developed a risk score for new-onset AF that would work in a doctor's office, or a person could use it to figure out their risk of AF," she explains.

The risk factors for AF include older age, being male, being overweight, hypertension, having a heart murmur, and a history of heart failure.

"These have previously been described, but not put together in a risk score," she notes.

Risk Factors Can Be Predictive

For the study, Dr. Benjamin's team, which included Dr. Renate Schnabel from the Johannes Gutenberg-University in Mainz, Germany, collected data on 4,764 people who participated in the Framingham Heart Study.

These individuals were ages 45 to 95 and did not have AF. The selection of people for the study was made from examinations done between June 1968 and September 1987.

Over 10 years of follow-up, 10 percent of the people developed AF. The strongest factors that predicted the risk of developing AF were age, sex, weight, high blood pressure, being treated for high blood pressure, heart murmur, and heart failure.

In addition, researchers found that the time between the P and R waves (PR interval), as seen on an electrocardiogram, was also a significant predictor of AF. The risks associated with AF were also found to vary with age. For example, those over 65 were more than 15 times more likely to develop AF than people under 65, the researchers note.

Promise for Preventing AF Someday

This risk score may help physicians and patients determine the risk for AF, says Dr. Benjamin. More important, this risk score might help doctors develop a way to prevent the condition.

"Before you can prevent something, you have to know how to predict it," explains Dr. Benjamin. This risk score will be useful first to help patients understand their risk, second to provide information for clinical trials, and third to evaluate other ways of predicting AF.

Dr. David Brieger, at the University of Sydney in Australia and author of an accompanying journal comment, says this study could be a first step in finding a way to prevent AF.

"It may be possible to identify strategies, pharmacologic and others such as lifestyle, to prevent the onset of atrial fibrillation in high-risk patients," says Dr. Brieger.

Atrial fibrillation is a potentially disabling condition that is increasing in frequency and placing an increased burden on health care resources, says Dr. Brieger.

"Preventing this condition would have immense value. Identifying patients at high risk of developing the condition is an important initial step in this process," he adds.

The Clinical Impact Remains Uncertain

Dr. Gregg C. Fonarow, at the University of California, Los Angeles, says it is not clear how this risk score would change clinical practice.

"While helpful from a research standpoint, the potential clinical utility of this risk score requires validation in other populations and further study," says Dr. Fonarow.

"It remains untested whether detection of increased risk of AF will result in any change in care or improve clinical outcomes."

Learning More about Heart Rhythm

One of the most common abnormal heart rhythms is premature ventricular beats, or PVCs.

PVCs occur when the ventricles beat sooner than they should.

This means that the ventricle is contracting and pumping out blood before the atrium above it has completely pumped its blood volume into the ventricle.

Most of the time, PVCs are harmless. In fact, almost everyone has them at one time or another.

However, if PVCs occur too frequently (more than several times per minute), the heart is unable to pump an adequate volume of blood to the body, which can cause symptoms such as weakness, fatigue, palpitations, or low blood pressure.

Other types of rhythm problems can have similar effects.

Problems may occur when the heart beats too fast, too slow, or with an irregular rhythm.

But whether the heart is beating too fast, too slow, or too irregularly, the effects are often the same as one or more of those described above. Some additional examples of rhythm problems include:

heart block - occurs when the electrical signal is delayed or blocked after leaving the SA node. There are several types of heart blocks, and each one has a distinctive electrocardiogram (ECG) tracing.

Some dysrhythmias, however, occur only intermittently, and cannot be seen on a routine ECG or on a more sophisticated type of ECG, such as a signal-averaged ECG or a Holter monitor procedure (a prolonged recording of the heart rhythm over 24 hours or longer).

If the physician suspects a problem with the heart's conduction system and cannot adequately diagnose the problem with other tests or procedures, then he/she may also decide that an electrophysiology study is appropriate.

An electrophysiology study(EP) is a more invasive test used to provoke arrhythmia in order to identify the cause and location of an abnormal electrical impulse.

Always consult your physician for more information.

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